U.S. patent number 7,445,574 [Application Number 11/714,288] was granted by the patent office on 2008-11-04 for drive axle with variable oil flow mechanism.
This patent grant is currently assigned to American Axle & Manufacturing, Inc.. Invention is credited to Frank C. Weith.
United States Patent |
7,445,574 |
Weith |
November 4, 2008 |
Drive axle with variable oil flow mechanism
Abstract
An axle assembly including a differential gear set having a ring
gear. The axle assembly includes a carrier assembly housing that
contains the differential gear set and an arcuate fence disposed
adjacent to the ring gear that connects to the carrier assembly
housing. A moveable plate slidingly connects to the arcuate fence.
The moveable plate has an open position, a closed position and a
plurality of positions therebetween. The closed position is closer
to the ring gear than the open position. The arcuate fence and/or
the moveable plate may reduce churning of the lubrication to
increase the cooling efficacy of the lubrication.
Inventors: |
Weith; Frank C. (Shelby
Township, MI) |
Assignee: |
American Axle & Manufacturing,
Inc. (Detroit, MI)
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Family
ID: |
36649682 |
Appl.
No.: |
11/714,288 |
Filed: |
March 5, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070149339 A1 |
Jun 28, 2007 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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11082250 |
Mar 16, 2005 |
7189178 |
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Current U.S.
Class: |
475/160; 74/467;
184/6.12 |
Current CPC
Class: |
F16H
57/0483 (20130101); F16H 57/0423 (20130101); Y10T
74/19991 (20150115) |
Current International
Class: |
F16H
57/04 (20060101) |
Field of
Search: |
;74/468 ;184/79
;475/160,220,88,90 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lorence; Richard M.
Assistant Examiner: Young; Edwin A.
Attorney, Agent or Firm: Harness, Dickey & Pierce,
P.L.C.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of U.S. patent application Ser.
No. 11/082,250 filed on Mar. 16, 2005 now U.S. Pat. No. 7,189,178.
The disclosure of the above application is incorporated herein by
reference.
Claims
What is claimed is:
1. An axle assembly, comprising: a housing defining a chamber
partially filled with fluid; a differential rotatably supported in
said chamber such that rotation of said differential causes flow of
said fluid; and a variable flow control mechanism disposed within
said chamber and having a plate supported for movement relative to
said differential and an actuator for moving said plate.
2. The axle assembly of claim 1 wherein said plate is moveable
between a first position relative to said differential for reducing
flow of said fluid and a second position relative to said
differential for increasing flow of said fluid.
3. The axle assembly of claim 2 wherein said plate is biased by a
biasing mechanism toward said second position.
4. The axle assembly of claim 1 wherein said plate is supported for
sliding movement relative to said differential on a fence member
secured to said housing.
5. The axle assembly of claim 4 wherein said housing includes an
axle carrier and a cover secured to said axle carrier, and wherein
said fence member is secured to at least one of said axle carrier
and said cover.
6. The axle assembly of claim 1 wherein said differential includes
a ring gear rotatably driven by a pinion shaft, and wherein said
plate is moveable between a first position adjacent to said ring
gear and a second position displaced from said ring gear, said
actuator operable to move said plate in response to a control
signal.
7. The axle assembly of claim 6 wherein said variable flow control
mechanism further includes a control system operable for generating
said control signal and actuating said actuator in response
thereto.
8. The axle assembly of claim 7 wherein said actuator includes an
electric motor.
9. The axle assembly of claim 7 wherein said control signal is
based on one of a fluid temperature within said chamber and a
rotational speed of said differential.
10. The axle assembly of claim 6 wherein said variable flow control
mechanism further includes a fence on which said plate is supported
for movement between its first and second positions.
11. The axle assembly of claim 10 wherein said housing includes an
axle carrier and a cover secured to said carrier, and wherein said
fence is secured to at least one of said carrier and said cover in
proximity to teeth on said ring gear.
12. An axle assembly, comprising: a housing partially filled with
lubricating fluid; a differential rotatably supported in said
housing and having a ring gear; and a plate supported by said
housing for movement relative to said ring gear between a first
position adjacent to said ring gear and a second position displaced
from said ring gear for varying the flow of said fluid caused by
rotation of said ring gear.
13. The axle assembly of claim 12 wherein said plate is biased by a
spring toward its second position.
14. The axle assembly of claim 12 further comprising a
power-operated actuator operable for moving said plate between its
first and second positions, and a control system for actuating said
actuator in response to a control signal.
15. The axle assembly of claim 14 wherein said control signal is
based on at least one of a fluid temperature within said housing
and a rotational speed of said differential.
16. The axle assembly of claim 12 wherein said housing includes an
axle carrier and a cover secured to said carrier, and wherein said
plate is supported for sliding movement relative to said ring gear
on a support member secured to at least one of said carrier and
said cover.
17. An axle assembly, comprising: an axle housing including a
carrier and cover interconnected to define a chamber partially
filled with a lubricating fluid; a differential rotatably supported
within said chamber and partially submerged in said fluid; and a
variable flow control mechanism supported from one of said carrier
and said cover within said chamber and having a plate moveable
relative to said differential between first and second
positions.
18. The axle assembly of claim 17 wherein said variable flow
control mechanism further includes an actuator for controlling
movement of said plate.
19. The axle assembly of claim 18 wherein said actuator is a
power-operated device operable in response to a control signal
generated by a control system.
20. The axle assembly of claim 19 wherein said control signal is
based on at least one of a fluid temperature within said chamber
and a rotational speed of said differential.
21. An axle assembly, comprising: an axle housing defining a
chamber; a differential rotatably supported within said chamber; a
lubricating fluid disposed in said chamber such that a portion of
said differential rotates through said fluid; a plate supported
within said chamber for movement between first and second positions
relative to said differential; and a power-operated actuator for
moving said plate between its first and second positions to vary
flow of said fluid that is generated in response to rotation of
said differential.
22. The axle assembly of claim 21 wherein said differential
includes a ring gear which rotates through said fluid, and wherein
said plate is moveable relative to said ring gear between its first
position adjacent thereto and its second position displaced
therefrom.
23. A method of controlling the flow of lubricating fluid within an
axle assembly, comprising: providing an axle housing having a
chamber partially filled with the fluid; rotatably supporting a
differential within said chamber such that a portion of said
differential rotates through the fluid; and moving a plate relative
to said differential to vary flow of the fluid generated in
response to rotation of said differential.
24. The method of claim 23 wherein said plate skims more of the
fluid off of said differential in a closed position located
proximate to said differential than in an open position displaced
from said differential.
25. An axle assembly, comprising: a housing defining a chamber; a
differential rotatably supported in said chamber; a drive mechanism
for driving said differential including a ring gear secured to said
differential and a pinion shaft driving said ring gear; a sump of
fluid retained within said chamber such that rotation of said ring
gear causes flow of said fluid; and a variable flow control
mechanism disposed between said ring gear and said fluid sump which
includes a plate supported in said housing for movement relative to
said ring gear, and an actuator for moving said plate.
26. The axle assembly of claim 25 wherein teeth on said ring gear
generate flow of said fluid in response to rotation of said ring
gear, and wherein said plate is moveable relative to said ring gear
between a first position adjacent to said teeth and a second
position displaced from said teeth.
27. The axle assembly of claim 26 wherein said variable flow
control mechanism further includes a spring for biasing said plate
toward one of its first and second positions, and wherein said
actuator is operable to move said plate in opposition to the
biasing of said spring.
Description
FIELD OF THE INVENTION
The present invention relates to a power transfer unit and, more
particularly, to a variable oil flow mechanism within an axle
assembly.
BACKGROUND OF THE INVENTION
The traditional axle assembly includes a carrier housing that
houses a differential gear set having a ring gear. The carrier
housing also includes a lubrication sump that contains a volume of
a lubricant to lubricate the differential gear set. As the ring
gear of the differential gear set turns, the ring gear can acts as
a pump thus moving the lubricant throughout the axle assembly.
While the lubricant can lubricate the differential gear set, the
lubricant can also cool the differential gear set. It will be
appreciated that as the rotational velocity of the gears of the
differential gear set increase, the lubricant can be chaotically
churned about the carrier housing. As the churning of the lubricant
increases, the ability of the lubricant to cool the differential
gear set decreases.
SUMMARY OF THE INVENTION
An axle assembly including a differential gear set having a ring
gear. The axle assembly includes a carrier housing that contains
the differential gear set and a variable oil flow mechanism. The
variable oil flow mechanism includes a fence disposed adjacent to
the ring gear that is connected to the carrier housing and a
moveable plate slidingly connected to the fence. The moveable plate
has an open position, a closed position and a plurality of
positions therebetween. The closed position is closer to the ring
gear than the open position.
Further areas of applicability of the present invention will become
apparent from the detailed description provided hereinafter. It
should be understood that the detailed description and specific
examples, while indicating the various embodiment of the invention,
are intended for purposes of illustration only and are not intended
to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the
detailed description, the appended claims and the accompanying
drawings, wherein:
FIG. 1 is a top view of an exemplary vehicle having an axle
assembly constructed in accordance with the teachings of the
present invention;
FIG. 2 is a perspective view of a carrier housing, a carrier
housing cover, a differential gear set and a variable oil flow
mechanism having a moveable plate and a fence constructed in
accordance with the teachings of the present invention and shown
with the fence connected to the carrier housing cover;
FIG. 3 is similar to FIG. 2 except that the fence is connected to
the carrier housing;
FIG. 4 is similar to FIG. 2 and shows an alternative configuration
of the fence and the moveable plate associated with a variable oil
flow mechanism constructed in accordance with the teachings of the
present invention;
FIG. 5A is a perspective view of the moveable plate, a spring and a
motor constructed in accordance with the teaching of the present
invention showing the moveable plate in an open position;
FIG. 5B is similar to FIG. 5A and shows the moveable plate in a
closed position;
FIG. 6 is a schematic of exemplary control system components
associated with the variable oil flow mechanisms of the present
invention; and
FIG. 7 is a flow chart of an exemplary control system for
controlling actuation of the variable oil flow mechanisms.
DETAILED DESCRIPTION OF THE VARIOUS EMBODIMENTS
The following description of the various embodiments is merely
exemplary in nature and is in no way intended to limit the
invention, its application or uses. As used herein, the term
module, submodule, control module and/or device refers to an
application specific integrated circuit (ASIC), an electronic
circuit, a processor (shared, dedicated, or group) and memory that
executes one or more software or firmware programs, a combinational
logic circuit, or other suitable components that provide the
described functionality. Moreover, vehicle controllers may
communicate with various vehicle systems using digital or analog
inputs and outputs and/or an automotive communications network
including, but not limited to, the following commonly used vehicle
communications network standards: CAN and SAE J1850.
With reference to FIG. 1, an exemplary vehicle 10 is shown with an
axle assembly 12 constructed in accordance with the teachings of
the present invention. The exemplary vehicle 10 includes an engine
14, a frame 16, a transmission 18, a driveshaft 20, a pair of
driven-wheels 22 and a pair of optionally-driven-wheels 24. The
engine 14 produces an output having a torque component in a manner
known in the art and transmits the output to the transmission 18.
The transmission 18 may reduce the rotational velocity and increase
the torque of the output produced by the engine 14. The
transmission 18 then transmits the torque to the axle assembly 12
through the driveshaft 20. The axle assembly 12 transmits the
torque via a differential gear set 26 to the pair of driven-wheels
22, which function to propel the vehicle 10. A variable oil flow
mechanism having a fence 28 with a moveable plate 30 coupled
thereto may be disposed adjacent to the differential gear set 26,
as below discussed in detail.
The optionally-driven-wheels 24 may connect to the transmission 18
in a manner known in the art (e.g., in a four-wheel and/or
all-wheel drive configuration). The axle assembly 12 may include a
plurality of constant-velocity joints 32 such that the axle
assembly 12 may be configured as an independent rear differential
assembly. More specifically, a carrier housing 34 may be coupled to
the frame 16 (e.g., with frame braces 36), allowing the pair of
driven-wheels 22 to move (other than rotate) independently of the
carrier assembly housing 34. Moreover, the optionally-driven-wheels
24 may connect to the transmission 18 via a plurality of constant
velocity joints 38 (e.g., in the four-wheel and/or all-wheel drive
configuration), allowing the optionally-driven-wheels 24 to move
(other than rotate) independently of the transmission 18. It will
be appreciated that the vehicle 10 may be constructed with a unit
body construction in lieu of a traditional rail frame (an example
of which is shown in FIG. 1) or may be constructed with
combinations of the unit body construction and the traditional rail
frame.
With reference to FIGS. 2, 3 and 4, the carrier assembly housing 34
is shown in accordance with the teachings of the present invention.
The carrier housing 34 contains the differential gear set 26. The
differential gear set 26 includes a ring gear 40 and side gears 42,
which attach to driveshaft flanges 44 in a manner known in the art.
Each of the driveshaft flanges 44 may connect to a half-shaft 46
(FIG. 1) for driving wheels 22 in a manner known in the art.
The carrier housing 34 also contains a volume of lubrication 48
contained in a lubrication sump 50. At least a portion of the
differential gear set 26 resides in the lubrication 48, as shown in
FIG. 2. More specifically, the ring gear 40 (or a portion thereof
as shown in FIG. 2) rotates through the lubrication 48. As the ring
gear 40 rotates through the lubrication 48, the ring gear 40 may
chaotically toss (i.e., churn) the lubrication 48 about the carrier
housing 34. It will be appreciated that the lubrication 48 may be
used to cool and lubricate the differential gear set 26 because,
among other things, the differential gear set 26 heats during use
due to friction between its respective components.
The more the lubrication 48 is churned and chaotically tossed about
the carrier housing 34, the less effective the lubrication 48 is at
cooling the differential gear set 26 and other components of the
axle assembly 12. In one example, the variable oil flow mechanism
is oriented such that the fence 28 is positioned adjacent to the
ring gear 40 to catch and/or skim the lubrication 48 off the ring
gear 40 and/or ring gear teeth 52, as the ring gear 40 rotates up
and out of the lubrication sump 50. Because at least a portion of
the lubrication 48 may strike the fence 28 instead of being churned
and chaotically tossed about the carrier housing 34, the
lubrication 48 may cool the differential gear set 26 relatively
more effectively.
The ring gear 40 of the differential gear set 26 is rotatably
driven by a pinion shaft 54 (FIGS. 3 and 4) in a manner known in
the art. It will be appreciated that as the speed of the engine 14
(FIG. 1) increases, the rotational speed of the driveshaft 20 (FIG.
1) increases for a given transmission gear ratio. As the rotational
speed of the driveshaft 20 increases, the rotational speed of the
pinion shaft 54 increases; this increases the rotational speed of
the ring gear 40. As the rotational speed of the ring gear 40
increases, the potential for the ring gear 40 to churn and
chaotically toss about the lubrication 48 increases.
The fence 28 may be disposed in a space 56 defined adjacent the
ring gear 40 between the carrier housing 34 and a carrier housing
cover 58. As the lubrication 48 is thrown against the fence 28, the
lubrication may drip and/or travel back down the fence 28 into the
lubrication sump 50. It will be appreciated that the reduced motion
(i.e., less churning and/or chaotic tossing) of the lubrication 48
compared to an implementation without the fence 28, allows the
lubrication 48 to cool the differential gear set 26 more
effectively. Moreover, the fence 28 may include a plurality of
drain holes 60 further allowing the lubrication 48 to drip back
into the lubrication sump 50, which may further promote cooling
efficacy by the lubrication 48.
It may be shown that the controlled return of the lubrication 48 to
the lubrication sump 50 (i.e., dripping down or traveling down the
fence 28) provides relatively better cooling efficacy of the
differential gear set 26 when compared to the axle assembly 12
without the variable oil flow mechanism. The slow dripping and/or
traveling down the fence 28 allows the lubrication 48 to cool more
readily as it returns to the lubrication sump 50. It will be
appreciated that the shape, size and position of the fence 28
relative to the ring gear 40 may be specific to each axle assembly
model and, as such, the size and configuration of the fence 28 may
vary accordingly.
In one example, the fence 28 may be arranged in relation to the
differential gear set 26 and the ring gear 40 in such a way that a
portion of the fence 28 is horizontal, as generally indicated by
reference number 62 (FIG. 3). By way of the above example, the
horizontal portion 62 of the fence 28 may be parallel to a pinion
shaft rotational axis 64. In another example, the fence 28 may be
arranged in relation to the differential gear set 26 and the ring
gear 40 in such a way that a portion of the fence 28 is slanted
(i.e., not horizontal), as generally indicated by reference number
66 (FIG. 4). In the various examples, various portions of the fence
28 may bend around various portions of the differential gear set 26
and, as such, the fence 28 may have one or more arcuate
portions.
In one example, the fence 28 may connect to the carrier housing 34,
as illustrated in FIG. 3. By way of the above example, the fence 28
may attach to the carrier housing 34 at at least one fence
attachment point 68. The fence 28 may attach to the carrier housing
34 using mechanical fasteners, chemical bonding, a molded press-fit
connection (e.g., a lip press-fit into a groove) and/or
combinations thereof.
In one example, the fence 28 may connect to the carrier housing
cover 58, as illustrated in FIG. 2. By way of example, the fence 28
may attach to the carrier housing cover 58 or more fence attachment
points 70. It will be appreciated that the fence attachment points
70 may coincide, for example, with apertures 72 formed in the
carrier housing cover 58, which may receive fasteners 74.
Complimentary apertures 76 formed in the carrier housing 34 may
also receive the fasteners 74 to attach the carrier housing cover
58 to the carrier housing 34 in a manner known in the art. By way
of the above example, the fence 28 may also be attached to the
carrier housing cover 58 using chemical bonding, a molded press-fit
connection (e.g., the lip and the groove) and/or combinations
thereof.
With reference to FIG. 5A and FIG. 5B, the movable plate 30 is
slidingly attached to the fence 28. The movable plate 30 can slide
relative to the ring gear teeth 52 and thus move between an open
position 78 (FIG. 5A), a closed position 80 (i.e., closer to the
ring gear) (FIG. 5B) and a plurality of positions therebetween.
When the movable plate 30 is in its closed position 80, for
example, a face 82 of the moveable plate 30 may be about 3
millimeters (about 0.12 inches) away from a top face 84 of each of
the ring gear teeth 52. When the movable plate 30 is in the open
position 78, the face 82 of the movable plate 30 may be at least
about 20 millimeters (about 0.79 inches) away from the top face 84
of the ring gear teeth 52. It will be appreciated that the distance
between the face 82 of the movable plate 30 and top face 84 of the
ring gear teeth 52 may be specific to each axle assembly model.
A pair of channel brackets 86, a spring 88 and a motor 90 may be
mounted to the fence 28 and connect to the movable plate 30. The
movable plate 30 can slide in the pair of channel brackets 86 as it
moves between the open position 78 (FIG. 5A) and the closed
position 80 (FIG. 5B). The spring 88 can couple the moveable plate
30 to the fence 28. It will be appreciated that more than one
spring may be used. Whether the moveable plate 30 is in the open
position 78, the closed position 80 or the plurality of positions
therebetween, the spring 88 applies a force to the moveable plate
80. By constantly applying the force to the moveable plate 30, the
spring 88 reduces vibrations experienced by the moveable plate 30
and the fence 28.
The motor 90 can have a gear 92 (e.g., a spur gear) connected
thereto. The gear 92 can mesh with a toothed rack 94 formed on the
moveable plate 30. By way of example, the motor 90 can rotate the
gear 92 to drive the moveable plate 30 between its open position 78
and its closed position 80, which may further elongate the spring
88 (i.e., further against the bias of the spring 88). It will be
appreciated that a default position 96 of the movable plate 30 is
in its open position 78. By way of example, the motor 90 may hold
the movable plate 30 in the closed position 80, the open position
78 and a plurality of positions therebetween but if the motor 90
were to fail, the spring 88 returns the movable plate 30 to its
open position 78.
The ring gear 40 has an axis of rotation 98 (FIG. 3) upon which the
ring gear 40 spins. To that end, one side 40a of the ring gear 40
is turning into the lubrication sump 50 while the other side 40b of
the ring gear 40 is coming up from the lubrication sump 50. It will
be appreciated that the side 40b of the ring gear 40 is rotating
out of the lubrication sump 50 is the side 40b of the ring gear 40
that may throw lubrication (i.e., churn and/or chaotically toss)
around the carrier assembly housing 34, thus reducing the cooling
efficacy of the lubrication 48. As such, the movable plate 30 may
be orientated on the side 40b of the ring gear 40 that is rotating
out of the lubrication sump 50. It will be appreciated that the
side 40b that is rotating out of the lubrication sump 50 is
dependent upon the direction of rotation of the ring gear 40 and,
as such, the fence 28 and/or the moveable plate 30 may be oriented
accordingly.
By way of the above examples, the fence 28 and the movable plate 30
may be fixedly mounted to the carrier housing cover 58. The cover
58 may be releaseably connected to the carrier housing 34. It will
be appreciated that the cover 58 can be removed to service, among
other things, the differential gear set 26. As such, the fence 28
and the cover 58 can be one unit such that removal of the cover 58
will remove the fence 28 from the carrier housing 34.
With reference to FIG. 6, the motor 90 and/or the movable plate 30
may be connected to a vehicle communications network (e.g., a CAN
bus system and/or other suitable vehicle communications systems)
via a communication link 100. An engine control module 102 may
communicate with a motor control module 104 via the communications
network. It will be appreciated that the above control modules 102,
104 may be sub-modules of an engine computer or specific module in
communication therewith. The motor control module 104 may
communicate with the engine control module 102 to determine various
vehicle and/or engine parameters including, but not limited to,
engine speed, transmission speed and/or gear, lubrication
temperature and/or ambient temperature.
In one example, the engine control module 102 may communicate with
a lubrication temperature sensor 106, an axle assembly temperature
sensor 108, a driveshaft rotational velocity sensor 110 and/or a
wheel rotational velocity sensor 112. The engine control module 102
may also communicate with the motor control module 104, which in
turn may communicate with the motor 90 that moves the moveable
plate 30. It will be appreciated that one or more of the
above-mentioned sensors 106, 108, 110 and 112 may directly and/or
indirectly communicate with the control module 102 and/or the motor
control module 104. Moreover, not all of the above-mentioned
sensors 106, 108, 110 and 112 need be present to implement the
various examples of the present invention.
The lubrication temperature sensor 106 may be located in the
carrier housing 34 (FIG. 1) and/or other portions of the axle
assembly 12. The lubrication temperature sensor 106 may detect a
lubrication temperature therein. The axle assembly temperature
sensor 108 may detect an axle assembly temperature. The axle
assembly temperature sensor 108 may detect a housing material
temperature (i.e., a metal temperature) or an air temperature
within the carrier assembly housing 34 and/or other portions of the
axle assembly 12. It will be appreciated that temperature may be
determined at various location within the axle assembly 12 (FIG.
1). It will also be appreciated that both the lubrication
temperature sensor 106 and the axle assembly temperature sensor 108
need not be used to make the various examples of the present
invention operable. In one example, the temperature determined by
the lubrication temperature sensor 106 may serve as proxy for axle
assembly temperature. In another example, the temperature
determined by the axle assembly temperature sensor 106 may serve as
proxy for lubrication temperature. As below explained, temperatures
of other components and/or fluid may serve as proxies for axle
assembly temperature and/or lubrication temperature.
The driveshaft rotational velocity sensor 110 may be located in the
transmission 18 and/or the carrier housing 34 (i.e., multiple
sensors). The driveshaft rotational velocity sensor 110 may detect
driveshaft rotational velocity directly, for example, with a Hall
Effect sensor or other suitable sensor. The driveshaft rotational
velocity sensor 110 may also detect driveshaft rotational velocity
indirectly, for example, by determining the driveshaft rotational
velocity based on engine speed and a transmission gear.
The wheel rotational velocity sensor 112 may be located near the
driven-wheels 22 (FIG. 1) and/or the optionally-driven-wheels 24
(FIG. 1). For example, the wheel rotational velocity sensor 112 may
detect wheel rotational velocity via an anti-lock brake sensor in a
manner known in the art. In another example, the wheel rotational
velocity sensor 112 may detect wheel rotational velocity be
detecting the rotational velocity of a component to which a wheel
is coupled (e.g., the ring gear 40 is coupled to one of the
driven-wheels 22). It will be appreciated that multiple wheel
rotational velocity sensors 112 may be employed to communicate the
rotational velocity of each wheel to the engine control module 102
and/or the motor control module 104.
The motor 90 can adjust the position of the movable plate 30 based
on engine speed, lubrication temperature, axle assembly
temperature, driveshaft, rotational velocity, wheel rotational
velocity, transmission speed and/or combinations thereof. It will
be appreciated that specific axle assembly models may dictate
additional factors and variables that can effect the positioning of
the movable plate 30. In one example, the motor control module 104
may command the motor 90 to move the moveable plate 30 based on
driven wheel rotational velocity and axle assembly temperature. In
another example, the motor control module 104 may command the motor
90 to move the moveable plate 30 based on driveshaft rotational
velocity and axle assembly temperature. When the driven wheel
rotational velocity, the driveshaft rotational velocity and/or axle
assembly temperature increases, the movable plate 30 can be moved
toward the ring gear 40. It will be appreciated that as the driven
wheel rotational velocity increases the churning and/or tossing of
the lubrication 48 may also increase. To increase the cooling
efficacy of the lubrication 48, the movable plate can be urged
toward the teeth 52 of the ring gear 40 thus further reducing
churning losses of the lubricant.
In one example, the movable plate 30 can move sufficiently close to
the teeth 52 of the ring gear 40 to at least partially skim the
lubricant off the face of each tooth 52 of the ring gear 40 before
the ring gear 40 is able to throw (i.e. churn and/or toss) the
lubrication 48 around the carrier housing 34. When the driven wheel
rotational velocity, the driveshaft rotational velocity and/or axle
assembly temperature is reduced, the motor control module 104 can
command the motor 90 to move the movable plate 30 toward its open
position 78. In another example, when the engine 14 is turned off,
the movable plate 30 can be moved to its open position 78. In a
further example, when the driven wheel rotational velocity and/or
driveshaft velocity is increased but the axle assembly temperature
and/or lubrication temperature remains relatively low, the movable
plate can remain in its open position 78.
With reference to FIG. 7, an exemplary control system 200 is
illustrated in accordance with the teachings of the present
invention. In step 202, the control system 200 determines if the
system is ready. When the control system 200 determines that the
system is ready, it continues to step 204. When the control system
200 determines that the system is not ready, it continues to the
below-described step 218. The control system 200 determines if the
system is ready by, for example, determining if any system faults
have been communicated to the control module 102, via the vehicle
communications network (e.g., the CAN bus system) such as, but not
limited to, an electrical problem, an inability to detect sensors
and/or engine trouble. Control system 200 may also determine
whether the transmission 18 (FIG. 1) is in a forward gear (e.g.,
drive and/or 1st gear, second gear etc.). In one example, control
system 200 may determine that the system is not ready unless the
transmission 18 is in the aforementioned forward gears.
In step 204, control system 200 determines an axle assembly
temperature. In one example, the axle assembly temperature may be
determined from the axle assembly temperature sensor 108 (FIG. 6).
In another example, the axle assembly temperature may be determined
from the lubrication temperature sensor 106 (FIG. 6). In a further
example, the axle assembly temperature may be determined from an
estimate of the axle assembly temperature based on other engine
temperatures and the duration at which the differential gear set 26
has been rotating. More specifically, a base engine temperature can
be determined from the engine 14 (e.g., a coolant and/or oil
temperature). The engine control module 102 may then estimate,
based on an elapsed time at a certain engine speed, how much the
differential gear set 26 may have heated the axle assembly 12.
Based on the engine temperature and the estimated heat produced in
the axle assembly 12, the engine control module 102 may estimate
the axle assembly temperature. From step 204, control system 200
continues to step 206.
In step 206, control system 200 determines a driveshaft rotational
velocity. Control system 200 may determine the driveshaft
rotational velocity by communicating with the driveshaft rotational
velocity sensor 110 (FIG. 6). In one example, control system 200
may determine the engine speed and the gear in which the
transmission 18 is engaged and thus, determine the rotational
velocity of the driveshaft 20 based on the engine 14 (FIG. 1) and
the transmission 18 (FIG. 1). From step 206, control system 200
continues to step 208.
In step 208, control system 200 determines a wheel rotational
velocity. Control system 200 may determine the wheel rotational
velocity by communicating with the wheel rotational velocity sensor
112 (FIG. 6). In one example, the wheel rotational velocity sensor
112 may detect the rotational velocity of the each of the
driven-wheels 22 (FIG. 1). In another example, the wheel rotational
velocity sensor 112 may detect the rotational velocity of all of
the wheels 22, 24 (FIG. 1). In a further example, the control
system 200 may determine the engine speed and the gear in which the
transmission is engaged and thus, determine the rotational velocity
of the output of the transmission (i.e., rotational velocity of the
driveshaft) based on known transmission gear ratios and engine
speeds. Based on the rotational velocity of the driveshaft, the
rotational velocity of the ring gear 40 may be determined. Based on
the rotational velocity of the ring gear 40, the rotational
velocity of one or more of the driven-wheels 22 may be determined.
From step 208, the control system 200 continues to step 210.
In step 210, control system 200 determines whether the axle
assembly 12 is warm enough. When control system 200 determines that
the axle assembly temperature is warm enough, it continues to step
212. When the control system 200 determines that the axle assembly
temperature is not warm enough, it continues to step 218. In one
example, the lubrication temperature may serve as a proxy for axle
assembly temperature and, as such, step 208 may determine whether
the lubrication temperature is warm enough. The axle assembly 12
may be warm enough when the lubrication temperature is about
100.degree. C. to about 120.degree. C. (about 212.degree. F. to
about 248.degree. F.). It will be appreciated that the operating
range of temperatures for the lubrication 48 in the carrier
assembly housing 34 can be based on a specific axle assembly
model.
In step 212, control system 200 determines whether the driveshaft
rotational velocity is high enough. When control system 200
determines that the driveshaft rotational velocity is high enough,
it continues to step 214. When control system 200 determines that
the driveshaft rotational velocity is not high enough, it continues
to step 218. In one example, the rotational velocity of the
driveshaft 20 (FIG. 1) is high enough when the driveshaft
rotational velocity is about 2,000 revolutions per minute. It will
be appreciated that the rotational velocity of the driveshaft 20,
as above-described, may be based on the gear in which the
transmission 18 (FIG. 1) is engaged and the engine speed. It will
further be appreciated that the rotational velocity may be based on
the axle assembly model and moreover be based on driving style and
in situ settings of the engine control module 102. More
specifically, control system 200 may determine (e.g., learn) that
driving style has departed from a nominal driving style and set a
lower driveshaft rotational velocity threshold.
In step 214, control system 200 determines whether the wheel
rotational velocity is high enough. When control system 200
determines that the wheel rotational velocity is high enough, it
continues to step 216. When control system 200 determines that the
driveshaft rotational velocity is not high enough, it continues to
step 218. It will be appreciated that the wheel rotational velocity
may be based on axle assembly model and moreover be based on
driving style and in situ settings of the control module 102. More
specifically, control system 200 may determine (e.g., learn) that
the driving style has departed from a nominal driving style and set
a lower wheel rotational velocity threshold. In one example, a
vehicle forward velocity of 60 miles per hour in a certain
transmission gear may provide a high enough wheel rotational
velocity.
In step 216, control system 200 positions the moveable plate 30
toward the teeth 52 of the ring gear 40 at a predetermined position
based on driven wheel rotational velocity, driveshaft rotational
velocity and/or axle assembly temperature. In one example, control
system 200 positions the moveable plate 30 based on additional
variables such, but not limited to, engine speed, transmission
speed, lubrication temperature, gear in which the transmission is
engaged, ambient temperature and/or combinations thereof. It will
be appreciated that the position of the moveable plate 30 relative
to the teeth 52 of the ring gear 40 may be based on an iterative
process of determining lubrication temperature, driveshaft
rotational velocity, wheel rotational velocity and other suitable
variables as the moveable plate 30 is moved closer to or further
from the teeth 52 of the ring gear 40. More specifically, control
system 200 may poll lubrication temperature and adjust the position
of the moveable plate 30 using suitable control logic (e.g., a PID
controller). In other examples, control system 200 can reference a
look up table based on lubrication temperature and/or driveshaft
rotational velocity. Based on the value determined in the look up
table, control can position the movable plate 30 to the
predetermined position.
In step 218, control system 200 moves the plate 30 to the open
position 78. The open position 78, as defined, is the position
farthest from the teeth 52 of the ring gear 40 relative to the
closed position 80. The closed position 80 is defined by the
position of the movable plate 30 that is closest to the teeth 52 of
the ring gear 40 relative the open position 78.
The description of the invention is merely exemplary in nature and,
thus, variations that do not depart from the gist of the invention
are intended to be within the scope of the invention. Such
variations are not to be regarded as a departure from the spirit
and scope of the invention.
* * * * *